Electrostatic copying machines of the type which utilize strip-type photoconductors, including a surface adapted to carry a developable electrostatic latent image, generally utilize dry developer materials for developing the latent image. Such developer materials normally include a toner material and a carrier material. For development purposes, the toner material is charged to a polarity opposite to that of the charge forming the latent image on the photoconductor. As a consequence, when the developer material is brought into contact with the image bearing surface of the photoconductor, toner material adheres to the image, thereby rendering the same visible, i.e., developed. Accordingly, copying machines of the aforesaid type are generally provided with some means for contacting the image bearing surface of the photoconductor with developer material from a readily available working supply of the same.
One of the known types of apparatus available for developing latent images is a magnetic-brush developer. For use with such developers, the carrier material content of the developer material is made of a magnetizable material, such as iron. A typical magnetic-brush developer includes a rotating applicator immersed in a working supply of developer material, and a moving magnet cooperative with the applicator for forming a magnetic field in a space between the applicator and magnet. Since pa photoconductor bearing the electrostatic latent image is also disposed in the field space, with the image surface facing the applicator; as the applicator urges developer material into the field space the field entrains the developer material disposed on the surface of the applicator. As applicator and magnet move in different directions relative to one another, the entrained developer material brushes the image bearing surface of the photoconductor, thereby developing the latent image. The developer material on the applicator is then returned directly to the working supply of developer material, mixed with the same and recycled.
To prevent the working supply of developer material from becoming gradually useless due to wear and tear of the carrier material content and continuous dissipation of the toner material content, the supply must be rejuvenated from time-to-time. This is normally done by adding developer material, including toner and/or carrier material, from a replenishing supply of the same, directly into the working supply of developer material and mixing the added material with the working supply along with the developer material returned to the working supply from the applicator.
In such systems the developer material returned to the working supply from the applicator is often insufficiently mixed with the working supply before being recycled for development purposes, and/or the developer material from the replenishing supply is insufficiently mixed with the working supply before being initially utilized. As a result, a given portion of an electrostatic latent image may be under-developed, over-developed or not developed; or a particular developed image, and/or successive developed images, may be unevenly shaded with toner material. Accordingly:
An object of the present invention is to provide an electrostatic copier including improved means for developing electrostatic latent images;
Another object is to provide improved apparatus for developing electrostatic latent images including means for collecting and mixing developer material;
A further object is to provide improved means for holding, carrying, collecting, feeding and blending developer materials in an electrostatic copier; to ensure having a uniformly bblended working supply of developer material available for developing electrostatic latent images; and
A still further object is to provide a process for developing electrostatic latent images including an improved method of mixing developer materials utilized in the process.